The invention is in the field of electronic reproduction technology and is directed to a device and to the operation thereof for automatically clamping film material onto the recording drum of a reproduction apparatus and for releasing the film material exposed by a recording element from the recording drum. In particular, the reproduction apparatus is a color scanner or color recorder.
In reproduction technology, color separations for multi-color printing are produced with color scanners or color recorders. To that end, color signals are first acquired by optoelectronic, trichromatic scanning of a chromatic original and these color signals are converted into color separation signals by a color correction. Sheet-shaped film materials, also referred to as film proofs or film sheets, are clamped on a recording drum of the color scanner or color recorder and are exposed point-by-point and line-by-line by a recording element that is modulated in brightness by the color separation signals. The exposed film proofs are released from the recording drum and are developed. The developed film proofs are the color separations for the multi-color printing.
The film proofs to be exposed and having different formats can already be present in the form of sheet film material that is taken from a sheet film cassette for clamping or that is cut-off from roll film material situated in a roll film cassette before the clamping.
In traditional color scanners or color recorders, the film proofs to be exposed are manually clamped onto the recording drum and are fixed thereat either with adhesive tape or with a vacuum suction.
It is required for an effective and economical use of a color scanner or color recorder to enhance the efficiency, particularly by shortening the preparation and adjustment times at the color scanner as compared to the times required for the actual film exposure. The preparation and adjustment times, for example, can be reduced in that the optimum adjustment parameters for a good reproduction are calculated by an operator in a prior process on the basis of work preparation devices (AV devices) and are stored and are then transferred into the color scanner in a short time immediately before the film exposure. At the same time, as many work steps as possible that are to be normally executed by the operator must be automated, for example the clamping and releasing of the film proofs onto or, respectively, from the recording drum.
In what are referred to as bright room devices, i.e. devices that do not work in dark rooms but under day light, it must also be taken into consideration that the removal of the film material from the supply cassette, the conveying thereof to the recording drum and the clamping and release must occur under exclusion of light.
German Patent 22 09 515 already discloses a device for clamping and releasing sheet-shaped film proofs onto or, respectively, from the recording drum of a color scanner. The film proofs to be exposed, which are provided with registration perforations and are situated in a sheet film cassette, have their registration perforations hooked over the registration pins situated on the recording drum on the basis of a manually actuatable roller and lever mechanism, are pulled from the sheet film cassette by turning the recording drum and are fixed on the recording drum by vacuum. After the exposure, the film proofs are lifted off from the drum surface by the roller and lever mechanism and are conveyed back into the sheet film cassette.
The device disclosed by German Patent 22 09 515 has the disadvantage that only film proofs provided with registration perforations and having given formats can be clamped and that the clamping and release can only occur with the collaboration of the operator.
US-A-4,268,841 discloses another electronic reproduction device that already comprises a means for automatically clamping sheet-shaped recording material on a recording drum, for vacuum suctioning of the recording material against the recording drum, and for automatically releasing the exposed recording material from the recording drum. The sheet-shaped recording material is automatically conveyed from a supply station via a conveyor means to the recording drum, is wound around the recording drum with the assistance of an annular channel between drum surface and housing wall and is fixed thereat by the vacuum suctioning. After the exposure, the recording material is likewise automatically released from the recording drum and is supplied to a discharge opening in the device for further processing.
The device disclosed by U.S. Pat. No. 4,268,841 likewise has the disadvantage that only sheet-shaped recording material can be clamped and released and that no specific measures are recited that guarantee a friction-free, automatic execution of the clamping and releasing.
DE-A-32 30 676 discloses a vacuum clamping means that employs a combination of pneumatic and mechanical components for fixing sheet-shaped recording material on a recording drum.
What is achieved by adding individual groups of suction holes or rows of suction holes is that recording material of different formats can be clamped without great vacuum losses. Means for controlling the valves and for conveying the recording material to or from the recording drum are not recited.
The device disclosed by DE-A-32 30 676 thus had the disadvantage that the feed of the sheet-shaped recording material must occur manually and that the switching of the groups or rows of suction holes does not occur automatically, dependent on the clamping and releasing event and/or on the respective format of the recording material to be clamped.
The tendency in reproduction technology is toward the employment of unperforated roll film material and to cut off the respectively required film lengths from the roll film material and to clamp it. Added thereto is the desire to be able to clamp and release arbitrary formats. Practice has shown that it is difficult to manually clamp, in particular, large-format film proofs onto the recording drum exactly and fold-free. The exact and smooth clamping of the film proofs, however, is an indispensable prerequisite for the exposure of exactly registered color separations and for the production of qualitatively high-grade multi-color prints.